For years, the only hearts doctors could use for transplants came from brain-dead donors who still had blood pumping through their veins. If the heart stopped on its own, it wasn’t used. But that may soon change, thanks to experimental procedures in Australia and England that have successfully transplanted a “dead heart” into a living body.

First performed last October in Sydney and repeated this month for the first time in Europe, the procedure calls for a non-beating heart to be restarted while still in the donor’s body. After doctors monitor it and determine that it’s still healthy, they move it to a “heart-in-a-box machine,” which keeps it warm and beating, in a nutrient-rich solution. The heart remains in the machine for the several hours between extraction and transplantation.

The patients who have received the once-dead hearts are strong and healthy. “This is a phenomenal achievement,” Simon Messer of Cambridge’s Papworth Hospital said to The Guardian. “People who previously would not get a heart transplant will now be able to have them.”

Indeed, the “dead heart” technique has the potential to dramatically increase the number of hearts available for transplant. Another doctor told TheGuardian it could increase heart transplants by 25 percent in the U.K. alone. In the U.S., the device is still not approved for use; according to the manufacturer of the “heart-in-a-box,” it is “under clinical investigation.” (That's typical for medical devices — in recent years, they're more likely to be tested experimentally in Europe or Asia while navigating the more lengthy U.S. approval process.)

There is a need, though, for technology like this in the U.S., where fewer than 10 percent of the people who need heart transplants each year receive them. When the device arrives Stateside, “dead hearts” won’t just help correct the quantity problem facing heart-transplant patients, but the quality problem. A recent study revealed that in 2010 only 32 percent of hearts available for transplant were deemed worthy of putting in a patient's body. This isn't the only way that medical pioneers are trying to increase the supply of hearts, either: Earlier this year, a patient in France was able to go home with an artificial heart beating in his chest.